[v3,04/28] ASoC: Add SOC USB APIs for adding an USB backend

diff --git a/include/sound/soc-usb.h b/include/sound/soc-usb.h
new file mode 100644
index 000000000000..378992ea07bd
--- /dev/null
+++ b/include/sound/soc-usb.h
@@ -0,0 +1,35 @@ 
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#ifndef __LINUX_SND_SOC_USB_H
+#define __LINUX_SND_SOC_USB_H
+
+/**
+ * struct snd_soc_usb
+ * @list - list head for SND SOC struct list
+ * @dev - USB backend device reference
+ * @component - reference to DAPM component
+ * @connection_status_cb - callback to notify connection events
+ * @priv_data - driver data
+ **/
+struct snd_soc_usb {
+	struct list_head list;
+	struct device *dev;
+	struct snd_soc_component *component;
+	int (*connection_status_cb)(struct snd_soc_usb *usb, int card_idx,
+				int connected);
+	void *priv_data;
+};
+
+int snd_soc_usb_connect(struct device *usbdev, int card_idx);
+int snd_soc_usb_disconnect(struct device *usbdev);
+void snd_soc_usb_set_priv_data(struct device *dev, void *priv);
+void *snd_soc_usb_get_priv_data(struct device *usbdev);
+
+struct snd_soc_usb *snd_soc_usb_add_port(struct device *dev, void *priv,
+			int (*connection_cb)(struct snd_soc_usb *usb, int card_idx,
+			int connected));
+int snd_soc_usb_remove_port(struct device *dev);
+#endif
diff --git a/sound/soc/Makefile b/sound/soc/Makefile
index 507eaed1d6a1..3305ceb59d84 100644
--- a/sound/soc/Makefile
+++ b/sound/soc/Makefile
@@ -1,5 +1,5 @@ 
 # SPDX-License-Identifier: GPL-2.0
-snd-soc-core-objs := soc-core.o soc-dapm.o soc-jack.o soc-utils.o soc-dai.o soc-component.o
+snd-soc-core-objs := soc-core.o soc-dapm.o soc-jack.o soc-usb.o soc-utils.o soc-dai.o soc-component.o
 snd-soc-core-objs += soc-pcm.o soc-devres.o soc-ops.o soc-link.o soc-card.o
 snd-soc-core-$(CONFIG_SND_SOC_COMPRESS) += soc-compress.o
 
diff --git a/sound/soc/soc-usb.c b/sound/soc/soc-usb.c
new file mode 100644
index 000000000000..4293451cdd49
--- /dev/null
+++ b/sound/soc/soc-usb.c
@@ -0,0 +1,180 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+#include <linux/of.h>
+#include <linux/usb.h>
+#include <sound/soc.h>
+#include <sound/soc-usb.h>
+#include "../usb/card.h"
+
+static DEFINE_MUTEX(ctx_mutex);
+static LIST_HEAD(usb_ctx_list);
+
+static struct device_node *snd_soc_find_phandle(struct device *dev)
+{
+	struct device_node *node;
+
+	node = of_parse_phandle(dev->of_node, "usb-soc-be", 0);
+	if (!node)
+		return ERR_PTR(-ENODEV);
+
+	return node;
+}
+
+static struct snd_soc_usb *snd_soc_find_usb_ctx(struct device *dev)
+{
+	struct device_node *node;
+	struct snd_soc_usb *ctx = NULL;
+
+	node = snd_soc_find_phandle(dev);
+	if (IS_ERR(node))
+		return NULL;
+
+	mutex_lock(&ctx_mutex);
+	list_for_each_entry(ctx, &usb_ctx_list, list) {
+		if (ctx->dev->of_node == node) {
+			of_node_put(node);
+			mutex_unlock(&ctx_mutex);
+			return ctx;
+		}
+	}
+	of_node_put(node);
+	mutex_unlock(&ctx_mutex);
+
+	return NULL;
+}
+
+/**
+ * snd_soc_usb_get_priv_data() - Retrieve private data stored
+ * @dev: device reference
+ *
+ * Fetch the private data stored in the USB SND SOC structure.
+ *
+ */
+void *snd_soc_usb_get_priv_data(struct device *dev)
+{
+	struct snd_soc_usb *ctx;
+
+	ctx = snd_soc_find_usb_ctx(dev);
+	if (!ctx) {
+		/* Check if backend device */
+		list_for_each_entry(ctx, &usb_ctx_list, list) {
+			if (dev->of_node == ctx->dev->of_node)
+				goto out;
+		}
+		ctx = NULL;
+	}
+out:
+	return ctx ? ctx->priv_data : NULL;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_get_priv_data);
+
+/**
+ * snd_soc_usb_add_port() - Add a USB backend port
+ * @dev: USB backend device
+ * @priv: private data
+ * @connection_cb: connection status callback
+ *
+ * Register a USB backend device to the SND USB SOC framework.  Memory is
+ * allocated as part of the USB backend device.
+ *
+ */
+struct snd_soc_usb *snd_soc_usb_add_port(struct device *dev, void *priv,
+			int (*connection_cb)(struct snd_soc_usb *usb, int card_idx,
+			int connected))
+{
+	struct snd_soc_usb *usb;
+
+	usb = devm_kzalloc(dev, sizeof(*usb), GFP_KERNEL);
+	if (!usb)
+		return ERR_PTR(-ENOMEM);
+
+	usb->connection_status_cb = connection_cb;
+	usb->dev = dev;
+	usb->priv_data = priv;
+
+	mutex_lock(&ctx_mutex);
+	list_add_tail(&usb->list, &usb_ctx_list);
+	mutex_unlock(&ctx_mutex);
+
+	return usb;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_add_port);
+
+/**
+ * snd_soc_usb_remove_port() - Remove a USB backend port
+ * @dev: USB backend device
+ *
+ * Remove a USB backend device from USB SND SOC.  Memory is freed when USB
+ * backend is removed.
+ *
+ */
+int snd_soc_usb_remove_port(struct device *dev)
+{
+	struct snd_soc_usb *ctx, *tmp;
+
+	mutex_lock(&ctx_mutex);
+	list_for_each_entry_safe(ctx, tmp, &usb_ctx_list, list) {
+		if (ctx->dev == dev) {
+			list_del(&ctx->list);
+			break;
+		}
+	}
+	mutex_unlock(&ctx_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_remove_port);
+
+/**
+ * snd_soc_usb_connect() - Notification of USB device connection
+ * @usbdev: USB bus device
+ * @card_idx: USB SND card instance
+ *
+ * Notify of a new USB SND device connection.  The card_idx can be used to
+ * handle how the USB backend selects, which device to enable offloading on.
+ *
+ */
+int snd_soc_usb_connect(struct device *usbdev, int card_idx)
+{
+	struct snd_soc_usb *ctx;
+
+	if (!usbdev)
+		return -ENODEV;
+
+	ctx = snd_soc_find_usb_ctx(usbdev);
+	if (!ctx)
+		return -ENODEV;
+
+	if (ctx->connection_status_cb)
+		ctx->connection_status_cb(ctx, card_idx, 1);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_connect);
+
+/**
+ * snd_soc_usb_disconnect() - Notification of USB device disconnection
+ * @usbdev: USB bus device
+ *
+ * Notify of a new USB SND device disconnection to the USB backend.
+ *
+ */
+int snd_soc_usb_disconnect(struct device *usbdev)
+{
+	struct snd_soc_usb *ctx;
+
+	if (!usbdev)
+		return -ENODEV;
+
+	ctx = snd_soc_find_usb_ctx(usbdev);
+	if (!ctx)
+		return -ENODEV;
+
+	if (ctx->connection_status_cb)
+		ctx->connection_status_cb(ctx, -1, 0);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_disconnect);